I just became a member this week. I have 1968, 1969, 1972 and 1975 Pontiac Illustration and Parts Catalogs so let's see if I can help. According to the 68 and 69 books, a 9786819 is a 2 groove 8" O.D. pulley used on 1968 V8s with power steering and without AC. If your car has AC, the pulley number should be 9788886 which has a 5 11/16" outer diameter.
